Conical cavity for surface resistance measurements of high temperature superconductors

A conically shaped cavity that intrinsically avoids mode-degeneration while maintaining the advantages of cylindrical resonators is presented. The cavity was applied to surface resistance measurements of YBaCuO thin films on MgO substrates at 18 GHz. The lowest measured value was 4.5 m Omega +or-2.1 m Omega for a 10 mm*10 mm laser ablated film at 77 K. An error analysis is carried out which leads to an accuracy of +or-2.1 m Omega for samples with 9 mm diameter and an accuracy of +or-0.5 m Omega for samples with 20 diameter.<
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